1. Field of the Invention
The present invention relates to a semiconductor device and a method for manufacturing the semiconductor device.
Note that the semiconductor device in this specification refers to all devices that can function by utilizing semiconductor characteristics, and electro-optic devices, semiconductor circuits, and electronic appliances are all semiconductor devices.
2. Description of the Related Art
Transistors formed over a glass substrate or the like are typically manufactured using amorphous silicon, polycrystalline silicon, or the like, as typically seen in liquid crystal display devices. Although transistors including amorphous silicon have low field-effect mobility, they can be formed over a larger glass substrate. On the other hand, although transistors including polycrystalline silicon have high field-effect mobility, they are not suitable for being formed over a larger glass substrate.
In contrast to the transistors manufactured using silicon, a technique in which a transistor is manufactured using an oxide semiconductor and applied to an electronic device or an optical device has attracted attention. For example, Patent Document 1 and Patent Document 2 each disclose a technique in which a transistor is manufactured using zinc oxide or an In—Ga—Zn—O-based oxide as an oxide semiconductor and such a transistor is used as a switching element or the like of a pixel of a display device.
In addition, Patent Document 3 discloses a technique by which an In—Ga—Zn—O-based oxide becomes oxynitride by introducing nitrogen into the film, whereby the In—Ga—Zn—O-based oxide is not only used in a transistor but can also be used as a transparent conductive film. This is because the conductance of the In—Ga—Zn—O-based oxide can be changed by introducing nitrogen thereto, according to Patent Document 3.